1. Field of Invention
The present invention relates to a thin film magnetic head having at least an inductive magnetic transducer for writing and a method of manufacturing the same.
2. Description of Related Art
In recent years, an improvement in performance of a thin film magnetic head has been demanded in accordance with an increase in surface recording density of a hard disk drive. As a thin film magnetic head, a composite thin film magnetic head in which a recording head having an inductive-type magnetic transducer for writing and a reproducing head having a magnetoresistive (hereinbelow, referred to as MR) element for reading are stacked is widely used.
In order to improve the recording density in the performance of the recording head, it is necessary to increase track density of a magnetic recording medium. For this purpose, it is necessary to realize a recording head of a narrow track structure in which the width on the air bearing surface of each of a bottom pole and a top pole formed while sandwiching a write gap is reduced to the order of a few microns to submicrons. In order to achieve this, semiconductor processing techniques are used.
Referring to FIGS. 30 to 35, as an example of a method of manufacturing a conventional thin film magnetic head, a method of manufacturing a composite thin film magnetic head will be described.
According to the manufacturing method, first, as shown in FIG. 30, an insulating layer 102 made of, for example, an aluminum oxide (Al2O3; hereinbelow, simply called xe2x80x9caluminaxe2x80x9d) is deposited in a thickness of about 5.0 to 10.0 xcexcm on a substrate 101 made of altic (Al2O3.TiC) or the like. Subsequently, a bottom shield layer 103 for a reproducing head is formed on the insulating layer 102. For example, alumina layer is then sputter-deposited in a thickness of 100 to 200 nm on the bottom shield layer 103 to form a shield gap film 104. Then, an MR film 105 for constructing an MR device for reproducing is formed in a thickness of tens nm on the shield gap film 104 and is patterned in a desired shape by high-precision photolithography. Then, lead layers (not shown) as lead electrode layers, which are electrically connected to the MR film 105, are formed on both sides of the MR film 105. After that, a shield gap film 106 is formed on the lead layers, the shield gap film 104, and the MR film 105, and the MR film 105 is buried in the shield gap films 104 and 106. Then, a top shield-cum-bottom pole (hereinbelow, referred to as a bottom pole) 107 made of a magnetic material such as nickel iron alloy (NiFe; hereinbelow, also simply called xe2x80x9cPermalloy (trade name)xe2x80x9d) used for both of the reproducing head and the recording head is formed on the shield gap film 106.
As shown in FIG. 31, on the bottom pole 107, a write gap layer 108 made of an insulating material such as alumina is formed. Further, a photoresist film 109 is formed in a predetermined pattern on the write gap layer 108 by high-precision photolithography. Then, on the photoresist film 109, a thin film coil 110 for an inductive-type recording head made of, for example, copper (Cu) is formed by plating or the like. Then, a photoresist film 111 is formed in a predetermined pattern by high-precision photolithography so as to cover the photoresist film 109 and the thin film coil 110. Then, in order to insulate the winding portions of the thin film coil 110 from each other, a heat treatment is conducted at a temperature of, for example, 250 degrees on the photoresist film 111.
As shown in FIG. 32, in a position rearward of the thin film coil 110 (the right side in FIG. 32), an opening 108a is formed by partially etching the write gap layer 108 in order to form a magnetic path, thereby exposing part of the bottom pole 107. Then, a top yoke-cum-top pole (hereinbelow, called a top pole) 112 made of a magnetic material having a high saturation magnetic flux density such as Permalloy is selectively formed so as to cover the exposed face of the bottom pole 107, the photoresist film 111 and the write gap layer 108.
As a method of forming the top pole 112, for example, as disclosed in Japanese Unexamined Patent Publication No. Hei 7-262519, a frame plating is used. When the top pole 112 is formed by using the frame plating, first, on the whole coil portion (hereinbelow, called an xe2x80x9capex portionxe2x80x9d) which is projected like a mountain and covered with the photoresist film 111, a thin electrode film made of, for example, Permalloy is formed by sputtering or the like. A photoresist is then applied on the electrode film, thereby forming the photoresist film. After that, the photoresist film is patterned by photolithography to form a frame (outer frame) for plating. Then, by using the electrode film formed beforehand as a seed layer, a plating film made of Permalloy is grown by plating, thereby forming the top pole 112.
The top pole 112, for example, has a shape in plane as shown in FIG. 35 which will be described hereinafter, and includes a yoke part 112a and a pole tip part 112b. The top pole 112 is in contact with and magnetically coupled to the bottom pole 107 in the opening 108a. Subsequently, by using part (pole tip part 112b) of the top pole 112 as a mask, both the write gap layer 108 and the bottom pole 107 are selectively etched by about 0.5 xcexcm through ion milling (refer to FIG. 34) and, after that, an overcoat layer 113 made of, for example, alumina is formed on the top pole 112. Finally, by machining and polishing, the track surface, that is, an air bearing surface 120 of the recording head and the reproducing head is formed, thereby completing a thin film magnetic head.
FIGS. 33 to 35 show the structure of the thin film magnetic head in a completed state. FIG. 33 shows a cross section of the thin film magnetic head in the direction perpendicular to the air bearing surface 120. FIG. 34 shows an enlarged cross section in the direction parallel to the air bearing surface 120 of the pole part. FIG. 35 shows a plane structure. FIG. 32 corresponds to a cross section taken along the line XXXIIxe2x80x94XXXII in FIG. 35. In FIGS. 33 to 35, it is omitted to graphically express the overcoat layer 113 and the like. In FIG. 35, with respect to the thin film coil 110 and the photoresist film 111, only their outlines are shown.
In FIGS. 33 and 35, xe2x80x9cTHxe2x80x9d denotes the throat height and xe2x80x9cMRHxe2x80x9d indicates the MR height. The xe2x80x9cthroat height (TH)xe2x80x9d is one of factors which determine the performance of the recording head and corresponds to a length from the position of the edge on the side closest to the air bearing surface 120 of the insulating layer (photoresist film 111) for electrically isolating the thin film coil 110 from the other conductive portions, that is, from the throat height zero position (THO position) to the position of the air bearing surface 120. In order to improve the performance of the recording head, it is necessary to rightsize the throat height (TH). The throat height (TH) is controlled by a polishing amount at the time of forming the air bearing surface 120. The xe2x80x9cMR height (MRH)xe2x80x9d denotes a length from the position of the edge on the side furthest from the air bearing surface 120 of the MR film 105, that is, the MR height zero position (MRHO position) to the position of the air bearing surface 120. The MR height (MRH) is also controlled by the polishing amount at the time of forming the air bearing surface 120.
Besides the throat height (TH) and the MR height (MRH) and the like, another factor that determines the performance of the thin film magnetic head is an apex angle (xcex8) shown in FIG. 33. The apex angle xcex8 is an average inclination angle of an inclined face close to the air bearing surface 120 of the photoresist film 111.
As shown in FIG. 34, a structure such that part of the write gap layer 108 and part of the bottom pole 107 are both etched in a self-aligned manner to the pole tip part 112b of the top pole 112 is called a trim structure. According to the trim structure, an increase in the effective track width due to expansion of the magnetic flux which occurs at the time of writing data to a narrow track can be prevented. xe2x80x9cP2Wxe2x80x9d shown in the drawing indicates the width of the portion having the trim structure (hereinbelow, simply called xe2x80x9cpole part 500xe2x80x9d), that is, the pole width (hereinbelow, also called xe2x80x9ctrack widthxe2x80x9d). The processing dimension of the pole width P2W depends on the width of a portion corresponding to the pole part 500 in a mask (photoresist film pattern in the above case) used at the time of performing an etching process to form the trim structure. xe2x80x9cP2Lxe2x80x9d shown in the drawing denotes the thickness of the pole tip part 112b constituting part of the pole part 500, that is, the pole length. As shown in FIG. 34, the lead layers 121 as the lead electrode layer electrically connected to the MR film 105 are provided on both sides of the MR film 105. In FIGS. 30 to 33, it is omitted to graphically express the lead layers 121.
As shown in FIG. 35, the top pole 112 has the yoke part 112a which occupies a major part of the top pole 112, and the pole tip part 112b which has an almost uniform width as the pole width P2W. In the connecting portion between the yoke part 112a and the pole tip part 112b, the outer edge of the yoke part 112a forms an angle xcex1 to a plane parallel to the air bearing surface 120. In the above-mentioned connecting portion, the outer edge of the pole tip part 112b forms an angle xcex2 to the plane parallel to the air bearing surface 120. For example, xcex1 is 45 degrees and xcex2 is 90 degrees. As described above, the pole tip part 112b serves as a mask when forming the trim structure of the pole part 500. As understood from FIGS. 33 and 35, the pole tip part 112b extends on the flat write gap layer 108 and the yoke part 112a extends on the apex portion.
Detailed structural characteristics of the top pole are described in, for example, Japanese Unexamined Patent Publication No. Hei 8-249614.
In the conventional thin film magnetic head having the structure as shown in FIG. 32, the magnetic flux generated by the thin film coil 110 at the time of recording information propagates through the top pole 112 from the yoke part 112a toward the pole tip part 112b and finally reaches the tip of the pole tip part 112b. The magnetic flux reached the tip of the pole tip part 112b generates a signal magnetic field to the outside. By the signal magnetic field, information is recorded onto a recording medium (not shown).
In order to assure the excellent overwrite characteristics of the thin film magnetic head, generally, it is necessary to smoothly and sufficiently supply the magnetic flux to the tip of the pole tip part 112b in the top pole 112 to sufficiently generate the above-described signal magnetic field.
In the conventional thin film magnetic head shown in FIG. 32, however, only the thin write gap layer 108 is provided between the pole tip part 112b of the top pole 112 and the bottom pole 107. Part of the magnetic flux flowed from the yoke part 112a toward the pole tip part 112b does not therefore reach the tip of the pole tip part 112b, but passes through the write gap layer 108 and propagates to the bottom pole 107. In the following, the propagation of the magnetic flux from the top pole 112 to the bottom pole 107 due to passing through the write gap layer 108 will be called xe2x80x9cleakage of magnetic fluxxe2x80x9d. Such a tendency is conspicuous especially in a region 112S, because a flow of the magnetic flux in the top pole 112 which heads in the downward direction in the drawing occurs in a part corresponding to the region 112S in the top pole 112.
The above-mentioned xe2x80x9cleakage of the magnetic fluxxe2x80x9d induces inconveniences as described below.
1) Due to the leakage of the magnetic flux from the top pole 112 to the bottom pole 107, the absolute volume of the magnetic flux propagating through the top pole 112 from the yoke part 112a to the pole tip part 112b decreases. In such a case, the magnetic flux generated by the thin film coil 110 cannot be sufficiently supplied to the tip of the pole tip part 112b. Consequently, the overwrite characteristic of the thin film magnetic head deteriorates severely.
2) Local concentration of the magnetic flux on the bottom pole 107 due to the leakage of the magnetic flux exerts an adverse influence on the reading operation of the thin film magnetic head. For example, when the magnetic flux concentrates on the bottom pole 107 more than necessary and part of the magnetic flux passes through the bottom pole 107 and reaches the MR film 105, the magnetic flux reached the MR film 105 acts as magnetic noises at the time of the reading operation of the reproducing head. Due to this, the normal reading operation of the thin film magnetic head is disturbed.
The invention has been achieved in consideration of the problems. An object is to provide a thin film magnetic head having an excellent overwrite characteristic by suppressing xe2x80x9cleakage of magnetic fluxxe2x80x9d and a method of manufacturing the same.
According to the invention, there is provided a thin film magnetic head comprising: a first magnetic layer and a second magnetic layer magnetically coupled to each other and having two magnetic poles which face each other with a gap layer having a flat surface in between near and in a recording-medium-facing surface to be faced with a recording medium, the first magnetic layer including a first magnetic layer portion having a uniform width portion which extends from the recording-medium-facing surface in a direction so as to be apart from the recording-medium-facing surface and which defines a recording track width of the recording medium; and a thin film coil provided between the first magnetic layer and the second magnetic layer with an insulating layer in between, wherein: a first non-magnetic layer pattern and a second non-magnetic layer pattern are disposed between the first magnetic layer portion of the first magnetic layer and the second magnetic layer in order from the second magnetic layer, the first non-magnetic layer pattern extending in a manner that a rear part thereof is connected to the insulating layer and a front end thereof terminates at a predetermined position recessed from the recording-medium-facing surface; and a second non-magnetic layer pattern extending in a manner that a rear end thereof is connected to the insulating layer and a front end thereof terminates at a position rearward of the front end of the first non-magnetic layer pattern.
In the thin film magnetic head of the invention, the first non-magnetic layer pattern and the second non-magnetic layer pattern are disposed between the first magnetic layer portion of the first magnetic layer and the second magnetic layer in order from the second magnetic layer. The front end of the second non-magnetic layer pattern is positioned rearward of the front end of the first non-magnetic layer pattern, and thereby a step is formed between the surface of the first non-magnetic layer pattern and the surface of the second non-magnetic layer pattern.
In the thin film magnetic head of the invention, the front end of the first non-pattern layer pattern may be positioned rearward of the uniform width portion in the first magnetic layer portion.
Furthermore, in the thin film magnetic head of the invention, a surface of the vicinity of the front end of the first non-magnetic layer pattern and a surface of the vicinity of the front end of the second non-magnetic layer pattern may be inclined with respect to a flat surface of the gap layer.
Furthermore, in the thin film magnetic head of the invention, at least the uniform width portion in the first magnetic layer portion may extend on the flat surface of the gap layer.
Furthermore, in the thin film magnetic head of the invention, the first magnetic layer portion may further comprise: at least two connection portions disposed so as to be separated from each other in a track width direction; and a coupling portion for magnetically coupling the uniform width portion to at least two connection portions. In such a case, in a region surrounded by the coupling portion and at least the two connection portions in the first magnetic layer portion, a third non-magnetic layer pattern connected to the insulating layer may be further disposed.
Furthermore, in the thin film magnetic head of the invention, the first magnetic layer may further include: a second magnetic layer portion which is magnetically coupled to the first magnetic layer portion so as to be partially overlapped with each other; and a third magnetic layer portion for magnetically coupling the second magnetic layer portion to the second magnetic layer.
Furthermore, in the thin film magnetic head of the invention, at least one part of both of the first magnetic layer and the second magnetic layer may be made of a material containing either a nickel iron alloy or an iron nitride, and may be made of a material containing an amorphous alloy such as a cobalt iron alloy, a cobalt iron nickel alloy or a zirconium cobalt iron alloy oxide.
According to the invention, there is provided a method of manufacturing a thin film magnetic head comprising: a first magnetic layer and a second magnetic layer magnetically coupled to each other and having two magnetic poles which face each other with a gap layer having a flat surface in between near and in a recording-medium-facing surface to be faced with a recording medium, the first magnetic layer including a first magnetic layer portion having a uniform width portion which extends from the recording-medium-facing surface in a direction so as to be apart from the recording-medium-facing surface and which defines a recording track width of the recording medium; and a thin film coil provided between these two magnetic layers with an insulating layer in between, wherein the method comprises: a step of selectively forming a first non-magnetic layer pattern so as to extend on the second magnetic layer so that a rear end thereof is connected to the insulating layer and a front end thereof terminates at a predetermined position recessed from the recording-medium-facing surface; a step of selectively forming a second non-magnetic layer pattern so as to extend on the first non-magnetic layer pattern so that a rear end thereof is connected to the insulating layer and a front end thereof terminates at a position rearward of the front end of the first non-magnetic layer pattern; and a step of forming the first magnetic layer portion so as to cover at least both of the first non-magnetic layer pattern and the second non-magnetic layer pattern.
In the method of manufacturing the thin film magnetic head of the invention, after the first non-magnetic layer pattern is selectively formed so as to extend on the second magnetic layer so that the rear end thereof is connected to the insulating layer and the front end thereof terminates at the predetermined position recessed from the recording-medium-facing surface, the second non-magnetic layer pattern is selectively formed so as to extend on the first non-magnetic layer pattern so that the rear end thereof is connected to the insulating layer and the front end thereof terminates at the position rearward of the front end of the first non-magnetic layer pattern. After that, the first magnetic layer portion is formed so as to cover both of the first non-magnetic layer pattern and the second non-magnetic layer pattern.
In the method of manufacturing the thin film magnetic head of the invention, a step of forming a photoresist pattern in the step of forming the first magnetic layer portion may include: a step of forming a photoresist layer so as to cover at least all of the flat surface of the gap layer, an inclined surface of the first non-magnetic layer pattern and an inclined surface of the second non-magnetic layer pattern; a first exposing step of selectively exposing a first region in the photoresist layer of a region extending from the flat surface of the gap layer to the inclined surface of the first non-magnetic layer pattern, the first region including a region corresponding to a planer shape of the uniform width portion of the first magnetic layer portion; a second exposing step of selectively exposing a second region in the photoresist layer of a region extending from the flat surface of the gap layer to the inclined surface of the second non-magnetic layer pattern, the second region corresponding to a planar shape of a part other than the uniform width portion of the first magnetic layer portion; and a step of forming the photoresist pattern by developing, in a lump, both of the first region and the second region in the photoresist layer. In such a case, it is preferable that the second exposing step is performed so that the first region and the second region are partially overlapped with each other.
Furthermore, in the method of manufacturing the thin film magnetic head of the invention, in the case where the first magnetic layer further includes: a second magnetic layer portion which is magnetically coupled to the first magnetic layer portion so as to be partially overlapped with each other; and a third magnetic layer portion for magnetically coupling the second magnetic layer portion to the second magnetic layer, the method may comprise: a step of forming the third magnetic layer portion and a coil connection pattern, simultaneously with the step of forming the first magnetic layer portion, the coil connection pattern being part of the thin film coil and being located at the end of the thin film coil; a step of forming a coil embedding layer as a preparatory layer of the insulating layer so as to cover at least all of the first magnetic layer portion, the third magnetic layer portion and the coil connection pattern; a step of planarizing a surface of the coil embedding layer by polishing until at least all of the first magnetic layer portion, the third magnetic layer portion and the coil connection pattern are exposed; and a step of forming the second magnetic layer portion so as to be in magnetic contact with exposed faces of each of the first magnetic layer portion and the third magnetic layer portion and, simultaneously, forming a conductive layer pattern so as to be in electrical contact with an exposed face of the coil connection pattern on the surface planarized by the polishing.
Furthermore, in the method of manufacturing the thin film magnetic head of the invention, as a material of forming at least one part of both of the first magnetic layer and the second magnetic layer, a material containing either a nickel iron alloy or an iron nitride may be used, and a material containing an amorphous alloy such as a cobalt iron alloy, a cobalt iron nickel alloy or a zirconium cobalt iron alloy oxide may be used.
Other and further objects, features and advantages of the invention will appear more fully from the following description.